Breakout detection method, continuous casting equipment operation method, and cast slab manufacturing method

Abstract

To provide a detection method of breakout, an operation method of a continuous casting facility, and a manufacturing method of a casting piece, which are capable of quickly detecting breakout in a transient state just after starting casting.SOLUTION: A detection method of breakout in a continuous casting facility 1 for steel monitors, at a start timing of casting, at least one of: the height of molten steel surface of a molten steel 2 to be supplied into a mold 13; and an opening deviation of a nozzle (sliding nozzle 11) for adjusting the supply amount of the molten steel 2 to be supplied into the mold 13, and detects the occurrence of breakout in at least one of the cases where: the height of molten steel surface is below an allowable height lower limit H0 in a time course after the start of casting; and the opening deviation is greater than an allowable deviation upper limit S0 in the time course after the start of casting.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for detecting a breakout, a method for operating a continuous casting facility, and a method for producing a cast slab. [Background technology]

[0002] Conventional breakout detection methods for steel continuous casting equipment use a camera attached directly below the mold to detect breakouts by judging changes in the amount of light captured by the camera based on a threshold, as described in Patent Documents 1 and 2. When a breakout is detected, measures such as stopping the supply of molten steel are taken immediately.

[0003] Various methods have also been proposed for predicting breakout. For example, Patent Document 3 discloses a method using temperature measuring devices. In the method of Patent Document 3, temperature measuring rows, each with a plurality of temperature measuring devices arranged horizontally, are arranged in multiple stages in the pouring direction below the molten metal surface of the mold of a continuous casting machine, and for any two stages of the rows, the temperature measuring devices arranged in the upper stage and the temperature measuring devices arranged in the lower stage are arranged on the same line. The measured values ​​of the temperature measuring devices in the upper and lower stages, which are on the same line, are then transmitted to a computing device, and a breakout is determined using the relationship between these measured values.

[0004] Furthermore, Patent Documents 4 and 5 disclose methods for determining breakout based on the deviation between the actual molten steel surface height and a threshold value for the molten steel surface height or the molten steel surface height to be controlled. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-25851 [Patent Document 2] Japanese Patent Application Publication No. 2-235561 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-154155 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-160525 [Patent Document 5] Japanese Patent Application Publication No. 47-21331 Summary of the Invention [Problem to be solved by the invention]

[0006] Various methods have been proposed for predicting breakouts, such as that in Patent Document 3, and although they can predict breakouts with a certain degree of accuracy based on signs of breakouts, they cannot completely predict all breakouts. For this reason, it has become necessary to detect breakouts using a camera installed directly below the mold, as in Patent Documents 1 and 2.

[0007] Furthermore, the methods disclosed in Patent Documents 1 to 3 were unable to predict or detect breakouts immediately after the start of casting for the following reasons: Breakout prediction methods are based on the mold temperature, but immediately after the start of casting, the mold is in a transient state as it rises from room temperature, and does not exhibit the same behavior each time. Therefore, it is difficult to predict a breakout immediately after the start of casting. Furthermore, because the amount of molten steel inside the mold is less than in normal conditions, even with a camera below the mold, the amount of light is insufficient, making it difficult to detect a breakout.

[0008] Furthermore, Patent Documents 4 and 5 attempt to detect breakout by setting a lower limit for the molten metal level using a certain threshold value or by creating a threshold value based on the deviation from the control value. Because this is based on the molten metal level, it is possible to detect breakout even in the transient state immediately after the start of casting. However, in the early stages of casting, the casting speed is often controlled using a certain pattern, and in such cases, the molten metal level is prone to hunting immediately after the casting speed is increased or immediately after the casting speed is made constant. Therefore, if a certain threshold value is used to make a judgment at the early stages of casting, it is necessary to set the threshold value according to the portion with large variations, and there is a problem that breakout detection time will be delayed if the threshold value is not set at the same time.

[0009] Therefore, the present invention has been made in light of the above-mentioned problems, and an object of the present invention is to provide a breakout detection method, a continuous casting equipment operating method, and a slab manufacturing method, which are capable of quickly detecting a breakout even in a transient state immediately after the start of casting. [Means for solving the problem]

[0010] (1) According to one aspect of the present invention, there is provided a breakout detection method for continuous steel casting equipment, which monitors at least one of the level of the molten steel supplied into a mold at the start of casting and the opening deviation of a nozzle that adjusts the amount of molten steel supplied into the mold, and detects that a breakout has occurred in at least one of the cases where the level of the molten steel falls below a lower limit H0 of the allowable height over time after the start of casting and where the opening deviation exceeds an upper limit S0 of the allowable deviation over time after the start of casting.

[0011] (2) In the configuration of (1) above, the allowable height lower limit H0 is calculated by the formula (1) based on a plurality of operational data from the start of past casting. H0=H-Aσ1 (1) where: H0: Lower limit of allowable height H: Average value of the melt level from multiple past operation data A: Coefficient σ1: Standard deviation of the mold surface height from multiple past operational data

[0012] (3) In the configuration of (1) or (2) above, the allowable deviation upper limit S0 is calculated by the formula (2) based on a plurality of operational data from the start of past casting. S0=S+Bσ2 (2) where: S0: Upper limit of allowable deviation S: Average value of nozzle opening deviation from multiple past operation data B: Coefficient σ2: Standard deviation of nozzle opening deviation from multiple past operational data

[0013] (4) In any one of the configurations (1) to (3) above, when the molten metal surface height is less than the allowable height lower limit H0 and the opening deviation exceeds the allowable deviation upper limit S0, it is detected that a breakout has occurred.

[0014] (5) According to one aspect of the present invention, there is provided a method for operating a continuous casting facility for continuously casting steel, comprising the steps of: There is provided a method for operating continuous casting equipment, which comprises detecting a breakout at the start of casting using the breakout detection method according to any one of the configurations (1) to (4) above, and interrupting the supply of molten steel to a mold when the breakout is detected.

[0015] (6) According to one aspect of the present invention, there is provided a method for producing a slab by continuously casting steel using the method for operating continuous casting equipment configured as described above in (5). [Effects of the Invention]

[0016] According to one aspect of the present invention, there are provided a breakout detection method, a continuous casting equipment operating method, and a cast slab manufacturing method, which are capable of quickly detecting a breakout even in a transient state immediately after the start of casting. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a configuration diagram showing a continuous casting facility according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the state of the continuous casting equipment at the start of casting. [Figure 3] 1 is a graph showing the allowable lower limit of height and the molten metal surface height at the time of breakout occurrence in an example. [Figure 4] 10 is a graph showing an upper limit of the allowable deviation and an opening deviation when a breakout occurs in an embodiment. [Figure 5] 10 is a graph showing the relationship between coefficient A and the number of detections in an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following detailed description, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations will be omitted. The drawings are schematic and may differ from the actual product. Furthermore, the embodiments shown below exemplify devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not specify the materials, structure, arrangement, etc. of component parts as described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0019] <Device configuration> FIG. 1 is a schematic diagram showing a continuous steel casting system 1 according to one embodiment of the present invention. The continuous casting system 1 includes a tundish 10, a sliding nozzle 11, a submerged nozzle 12, a mold 13, a plurality of support rolls 14, a molten steel level gauge 15, and a determination unit 16. In the continuous casting system 1, molten steel 2 contained in the tundish 10 is poured into the mold 13 via the sliding nozzle 11 and the submerged nozzle 12 and cooled to form a solidified shell at the interface between the mold 13 and the molten steel 2. The solidified shell is then withdrawn while supported by the support rolls 14 and further cooled with cooling water or the like to form a cast slab having a predetermined cross-sectional shape.

[0020] The sliding nozzle 11 has a plate 110 with holes formed therein, and controls the amount of molten steel 2 supplied from the tundish 10 to the mold 13 by sliding the plate 110. Specifically, the amount of molten steel 2 supplied is controlled by controlling the overlapping area between the holes in the plate 110 and the holes formed in the bottom of the tundish 10. The percentage of the sliding amount based on the relative position of the plate 110 in the sliding direction relative to the tundish 10 is referred to as the nozzle opening (%). For example, the nozzle opening may be defined as 100% when the holes in the plate 110 and the holes in the bottom of the tundish 10 completely overlap in the sliding direction, and as 0% when the holes do not overlap. The difference (fluctuation) in the nozzle opening after the start of casting from the average value of the nozzle opening over a certain period of time is referred to as the opening deviation. In this embodiment, the determination unit 16 calculates the opening deviation from the measurement results of the nozzle opening. The fixed period for calculating the average value of the nozzle opening degree is not particularly limited, but is preferably about 50 seconds.

[0021] The molten steel level gauge 15 is a measuring device that measures the height of the bath surface of the molten steel 2 in the mold 13. The measurement method of the molten steel level gauge 15 is not particularly limited as long as it is a known measurement method that can measure the height of the bath surface of the molten steel 2. For example, a vortex-type molten steel level gauge may be used as the molten steel level gauge 15. The height of the bath surface of the molten steel 2 is not particularly limited as long as it can determine the height position of the bath surface of the molten steel 2 in the mold 13, and may be, for example, the height (vertical distance) from the bottom surface of the mold 13 or a predetermined position inside the mold 13.

[0022] In the continuous casting equipment 1, the amount of molten steel 2 supplied to the mold 13 is adjusted by an adjustment mechanism (not shown). The adjustment of the amount of molten steel 2 supplied by this adjustment mechanism is performed by adjusting the nozzle opening based on the measurement result of the molten steel level gauge 15 so that the molten steel surface height is at a predetermined height.

[0023] The determination unit 16 is a calculation device such as a computer that detects breakout at the start of casting based on at least one of the nozzle opening degree and the molten metal level. The method of breakout detection by the determination unit 16 will be described in detail later.

[0024] In this embodiment, the period during which continuous casting is performed will be described as being divided into a casting start time and a steady casting time. The casting start time is the period from immediately after the start of continuous casting until the casting speed reaches the steady casting speed. The steady casting time is the period after the casting start time, that is, the period after the casting speed reaches the steady casting speed.

[0025] At the start of casting, continuous casting begins in the state shown in Fig. 2. As shown in Fig. 2, at the start of continuous casting, a dummy bar 17 is inserted into the continuous casting equipment 1, and the tip of the dummy bar 17 (dummy bar head) is placed in the mold 13. Then, with the tip of the dummy bar 17 positioned at the bottom of the mold 13, molten steel 2 is poured into the mold 13, thereby starting continuous casting. Then, after a predetermined time has elapsed since the molten steel 2 was poured, the dummy bar 17 is withdrawn. Then, the dummy bar 17 is separated from the slab at a predetermined position, and the casting speed is increased to a steady-state pouring speed.

[0026] At the start of casting, the judgment unit 16 continuously judges whether or not a breakout has occurred, thereby detecting a breakout. Note that, since a breakout cannot occur while the dummy bar 17 is present inside the mold 13, breakout detection is performed after the dummy bar 17 is withdrawn from the mold 13. If a breakout is detected, the supply of molten steel 2 to the mold 13 is stopped and casting is suspended. On the other hand, if a breakout is not detected, casting continues, and breakout detection is also continuously performed. The steady-state casting period is not particularly limited, and continuous casting is performed at a steady-state casting speed using a known continuous casting method.

[0027] <How to detect a breakout> The breakout detection method according to this embodiment will be described below. In this embodiment, as described above, the breakout detection method is performed based on at least one of the molten metal surface height and the opening deviation at the start of casting.

[0028] (Detection method based on the height of the molten metal surface) First, a method for detecting a breakout based on the molten steel level height will be described. In the detection method based on the molten steel level height, first, once continuous casting has started, the molten steel level meter 15 continuously measures the molten steel level height, and the measurement results are sent to the judgment unit 16, thereby monitoring the molten steel level height. Note that the molten steel level height may be measured as an actual distance (mm), or may be measured as an output value (%) of the molten steel level meter 15 corresponding to the actual distance.

[0029] Next, the determination unit 16 determines whether the measured molten metal level becomes less than the allowable height lower limit H0 over time after the start of casting. The determination unit 16 determines that a breakout has occurred if the molten metal level becomes less than the allowable height lower limit H0, and determines that a breakout has not occurred if the molten metal level becomes equal to or greater than the allowable height lower limit H0.

[0030] When a breakout occurs, the molten steel 2 breaks through the solidified shell and leaks out inside the continuous casting equipment 1, and the amount of molten steel 2 discharged from the mold 13 becomes greater than the amount of molten steel 2 supplied from the tundish 10, causing a drop in the molten steel surface height. Therefore, by setting a lower allowable height limit H0 as a threshold value for detecting a breakout, it is possible to detect a breakout in the early stages of casting. The lower allowable height limit H0 is a value obtained over time after the start of casting and is set for each elapsed time. For example, the lower allowable height limit H0 may be set for each measurement time interval of the molten steel surface height.

[0031] Furthermore, the allowable height lower limit H0 is preferably calculated using formula (1) based on multiple pieces of operational data from the start of past casting. The multiple pieces of operational data from the past are from conditions where no breakout occurred. Furthermore, the coefficient A is preferably between 5.0 and 10.0. H0=H-Aσ1 (1) where: H0: Lower limit of allowable height H: Average value of the melt level from multiple past operation data A: Coefficient σ1: Standard deviation of the mold surface height from multiple past operational data

[0032] The number of past operational data is preferably 50 or more in order to evaluate the variation (standard deviation) of the molten metal level height, while the number of past operational data is preferably 200 or less in order to deal with changes in patterns due to long-term fluctuations.

[0033] (Detection method based on opening deviation) Next, a method for detecting a breakout based on an opening deviation will be described. In the method for detecting a breakout based on an opening deviation, first, when continuous casting is started, the determination unit 16 continuously acquires the nozzle opening of the sliding nozzle 11 and calculates the opening deviation, thereby monitoring the opening deviation.

[0034] Next, the determination unit 16 determines whether the obtained opening deviation exceeds the upper limit of allowable deviation S0 over time after the start of casting. If the opening deviation exceeds the upper limit of allowable deviation S0, the determination unit 16 determines that a breakout has occurred, and if the opening deviation is equal to or less than the upper limit of allowable deviation S0, the determination unit 16 determines that a breakout has not occurred.

[0035] When a breakout occurs, the molten steel level drops as described above, and control is performed to increase the nozzle opening to increase the amount of molten steel 2 supplied from the tundish 10. The supply amount at this time is greater than when no breakout occurs, and the nozzle opening and opening deviation are also greater than usual. For this reason, by setting an allowable deviation upper limit S0 as a threshold value for detecting a breakout, it is possible to detect a breakout in the early stages of casting. Furthermore, the allowable deviation upper limit S0 is a value at the time elapsed after the start of casting, and is set for each elapsed time. For example, the allowable deviation upper limit S0 may be set for each time interval at which the molten steel level height is measured.

[0036] Furthermore, the allowable deviation upper limit S0 is preferably calculated using equation (2) based on multiple pieces of operational data from the start of past casting. The multiple pieces of operational data from the past are from conditions where no breakout occurred. Furthermore, the coefficient B is preferably between 5.0 and 10.0. S0=S+Bσ2 (2) where: S0: Upper limit of allowable deviation (%) S: Average value (%) of the opening deviation of multiple past operation data B: Coefficient σ2: Standard deviation of the opening deviation of multiple past operation data

[0037] Furthermore, the number of past operational data is preferably 50 or more in order to evaluate the variation (standard deviation) of the opening deviation, while the number of past operational data is preferably 200 or less in order to deal with changes in patterns due to long-term fluctuations.

[0038] (Detection method based on the level of the molten metal and the deviation of the opening) Furthermore, in this embodiment, a breakout may be detected based on both the molten metal level height and the opening deviation. In this case, the judgment unit 16 monitors both the molten metal level height and the opening deviation, and determines that a breakout has occurred when the molten metal level height is below the lower limit H0 of the allowable height and the opening deviation exceeds the upper limit S0 of the allowable deviation. On the other hand, if the molten metal level height is below the lower limit H0 of the allowable height and the opening deviation does not exceed the upper limit S0 of the allowable deviation, the judgment unit 16 determines that a breakout has not occurred. Note that it is also possible to monitor both the molten metal level height and the opening deviation, and determine that a breakout has occurred when the molten metal level height is below the lower limit H0 of the allowable height or the opening deviation exceeds the upper limit S0 of the allowable deviation.

[0039] As described above, in this embodiment, the occurrence of a breakout is detected by making a judgment based on at least one of the molten metal level height and the nozzle opening deviation. The judgment of the occurrence of a breakout is made based on at least one of the lower limit H0 of the allowable height and the upper limit S0 of the allowable deviation over time after the start of casting, so that the judgment can be made more accurately even in the transient state immediately after the start of casting than when making a judgment based on a fixed threshold value for the molten metal level height or the nozzle opening.

[0040] Furthermore, breakouts can be detected with high accuracy by setting the allowable height lower limit H0 using multiple pieces of past operational data and Equation (1), or by setting the allowable deviation upper limit S0 using multiple pieces of past operational data and Equation (2). Although the molten metal level is automatically controlled to a constant value, it is not actually constant and fluctuates within a certain range. Immediately after the start of casting, the speed pattern is similar due to constant operation. However, the molten metal level is prone to hunting immediately after the casting speed is increased or immediately after the casting speed is stabilized. Therefore, the average and variation of the molten metal level depend on the passage of time. Therefore, by setting the allowable height lower limit H0 and the allowable deviation upper limit S0 for each elapsed time, breakouts can be detected with higher accuracy. Furthermore, increased detection accuracy prevents false detections and improves productivity. Furthermore, compared to conventional detection methods such as those described in Patent Documents 3 and 4, breakouts can be detected more quickly, thereby reducing the impact of breakouts on production. Furthermore, compared to detection methods based on mold temperature, breakouts can be detected more directly, ensuring accurate detection.

[0041] Furthermore, unlike the molten metal surface height, the nozzle opening degree is not constant and depends on the size (width and thickness) of the mold 13 and various other conditions. For this reason, by making a judgment using the opening deviation, which is the fluctuation value from the average value for a certain period of time from the start of casting during the chance (unit of continuous casting) at which the judgment is made, it becomes possible to detect breakout using the same judgment criteria regardless of the size of the mold 13.

[0042] Furthermore, by detecting a breakout based on both the molten metal surface height and the opening deviation, it is possible to detect a breakout with higher accuracy.

[0043] Furthermore, in this embodiment, it is preferable to set the coefficients A and B in equations (1) and (2) to 5.0 or more and 10.0 or less, in other words, to detect a breakout when there is a fluctuation of 5 to 10 times the standard deviation of the molten metal level height and the opening deviation of the past operational data. By doing so, it is possible to determine a breakout without false detection.

[0044] <Modification> Although the present invention has been described above with reference to specific embodiments, it is not intended that the invention be limited by these descriptions. By referring to the description of the present invention, other embodiments of the present invention that include various modifications in addition to the disclosed embodiments will be apparent to those skilled in the art. Therefore, it should be understood that the embodiments of the invention set forth in the claims also encompass embodiments that include these modifications described herein, either alone or in combination.

[0045] For example, although the present embodiment describes a method for detecting breakouts, the present invention is not limited to such an example. The present invention can also be applied to methods for operating continuous casting equipment and methods for producing slabs. A method for operating continuous casting equipment according to one aspect of the present invention is a method for operating continuous casting equipment 1 that continuously casts steel, in which a breakout is detected at the start of casting using the breakout detection method according to the above embodiment. If a breakout is detected, the supply of molten steel 2 to the mold 13 is interrupted, and if a breakout is not detected, the supply of molten steel 2 to the mold 13 is continued. Furthermore, a method for producing slabs according to one aspect of the present invention continuously casts steel using the above method for operating continuous casting equipment 1. [Example]

[0046] The inventors of the present invention conducted an example, in which the allowable height lower limit H0 and the allowable deviation upper limit S0 were calculated from the past operational data of 200 runs using equations (1) and (2), and the mold surface height and the opening deviation at the time of breakout occurrence for two chances were compared.

[0047] Figure 3 shows the behavior of the mold surface height at the calculated lower limit H0 and the two chances of breakout versus time. In Figure 3, the vertical axis represents the mold surface height, and the horizontal axis represents the elapsed time (sec) from the start of dummy bar withdrawal. The mold surface height on the vertical axis represents the output value (%) of the molten steel level gauge 15 corresponding to the actual distance, and is controlled to be 45%. The horizontal axis represents the elapsed time from the start of pouring molten steel 2 into the mold 13 at -50 sec and from the start of dummy bar withdrawal at 0 sec. In the example shown in Figure 3, coefficient A is set to 7, i.e., the threshold value is set to 7 times the standard deviation of the average mold surface height. In the example shown in Figure 3, the timing when the mold surface height falls below the lower limit H0 occurs 10 to 20 seconds before the breakout detection that currently relies on the operator. This confirms that breakout detection can be performed accurately and quickly.

[0048] In the example shown in Figure 3, the threshold value fluctuates over time, reaching a maximum approximately 20 seconds after the start of casting. This is because the casting speed is changed approximately 20 seconds after the start of casting, causing large variations in the molten metal level. However, it was confirmed that the level then settles down to approximately one-third of the peak. Detection methods such as those described in Patent Documents 4 and 5 use a constant threshold value that matches the peak of the variation, forcing the threshold value to be set large over the entire time period. However, the detection method according to the above embodiment selects an optimal threshold value over time based on past operational data, enabling faster breakout detection than conventional detection methods.

[0049] Figure 4 shows the behavior of the calculated allowable deviation upper limit S0 and the opening deviation at the time of breakout occurrence for two chances over time. In Figure 4, the vertical axis represents the opening deviation, and the horizontal axis represents the elapsed time (sec) from the start of dummy bar withdrawal, as in Figure 3. The opening deviation on the vertical axis represents the difference from the average nozzle opening from -50 sec to 0 sec, and is shown for times after 0 sec. In the example shown in Figure 4, coefficient B is set to 4, i.e., a threshold value four times the standard deviation of the average opening deviation is assigned. Furthermore, the breakout occurrence chance in Figure 4 is the same as that in Figure 3. As is clear from Figure 4, it was confirmed that breakout can be detected more quickly when opening deviation is used than when using the molten metal level.

[0050] Furthermore, we investigated the effects of coefficients A and B in equations (1) and (2) on detection accuracy and the occurrence of false positives. Figure 5 shows the relationship between coefficients A and B and the number of breakout detections when coefficients A and B are varied from 1.0 to 10.0. In Figure 5, the graph labeled "Both" represents the case where both the mold level height and nozzle opening deviation detection methods were used. A breakout was detected only when a breakout was detected based on both the mold level height and nozzle opening deviation. In this investigation, the actual number of breakouts was two. It was confirmed that decreasing coefficients A and B reduced false positives but increased overdetection, while increasing coefficients A and B reduced overdetection but increased false positives. Therefore, it was confirmed that a coefficient A and B between 3.0 and 8 was appropriate for the equipment used in this example. Furthermore, in this example, when coefficients A and B were set to 4 and both the mold level height and nozzle opening deviation detection methods were used, the number of detections was two, confirming that there were no overdetection or false positives. Therefore, it was confirmed that the occurrence of a breakout can be detected with high accuracy by detecting both the molten metal surface height and the opening deviation. [Explanation of symbols]

[0051] 1. Continuous casting equipment 10 Tundish 11 Sliding Nozzle 110 Plate 12 Submerged Entry Nozzle 13 Mold 14 Support Roll 15 Molten steel level gauge 16 Judgment section 17 Dummyba 2. Molten steel

Claims

1. In a continuous steel casting facility, at least one of a level of a surface of molten steel to be supplied into a mold at the start of casting and an opening deviation of a nozzle that adjusts the amount of molten steel to be supplied into the mold is monitored, The molten metal level is lower than the allowable height lower limit H ０ If the opening deviation is less than the upper limit S of the allowable deviation over time after the start of casting, ０ In at least one of the cases where the price exceeds the limit, a breakout is detected. The method for detecting a breakout, wherein the allowable height lower limit H 0 and the allowable deviation upper limit S 0 are calculated based on a plurality of pieces of operational data from the start of past casting.

2. The allowable height lower limit H ０ The breakout detection method according to claim 1, wherein is calculated by the formula (1) based on the plurality of operation data at the start of casting in the past. H ０ =H-Aσ １ ・・・(1) where: H ０ : Lower limit of allowable height H: Average value of the molten metal surface height from multiple past operation data A: Coefficient σ1: Standard deviation of the molten metal level from multiple past operational data

3. The allowable deviation upper limit S ０ The breakout detection method according to claim 1, wherein is calculated by equation (2) based on the plurality of operation data at the start of casting in the past. S ０ =S+Bσ ２ ・・・(2) where: S ０ : Upper limit of allowable deviation S: Average value of nozzle opening deviation from multiple past operation data B: Coefficient σ ２ : Standard deviation of nozzle opening deviation from multiple past operational data

4. The molten metal surface height is the allowable height lower limit H ０ and the opening deviation is less than the allowable deviation upper limit S ０ The method for detecting a breakout according to claim 1, wherein the occurrence of a breakout is detected when the value of the first digit exceeds the value of the second digit.

5. A method for operating a continuous casting facility for continuously casting steel, comprising: At the start of casting, the breakout is detected using the breakout detection method according to any one of claims 1 to 4, A method for operating a continuous casting facility, comprising interrupting the supply of molten steel to the mold when the breakout is detected.

6. A method for producing a slab by continuously casting steel using the method for operating continuous casting equipment according to claim 5.

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